The protection of food from damage caused by microbes, spores, insects, and other similar sources is a major concern. Each year, economic losses of food and fiber due to damage from such sources is more than $100 billion. Currently, food items are preserved using a variety of methods, including refrigeration, fumigation with toxic chemicals, irradiation, biological control, heat exposure, and controlled atmosphere storage (a fruit industry technique that involves modifying the concentration of gases naturally present in the air).
The primary problem regarding food spoilage in public health is microbial growth. If pathogenic microorganisms are present, then growth can potentially lead to food-borne outbreaks and significant economic losses. Food safety concerns have been brought to the consumers' attention since the early part of the 20th century and those concerns have become even stronger today. Recent outbreaks from Salmonella and E. coli have increased the focus on food safety, including from a regulatory perspective. A report issued from National Research Council (NRC) in 1988 indicated that there were approximately 9,000 human deaths a year from 81 million annual cases of food poisoning. A recent study completed by the Centers for Disease Control and Prevention (CDC) estimated that food-borne diseases cause approximately 76 million illnesses, 325,000 hospitalizations and 5,000 deaths annually in the US. Those numbers reveal the dramatic need for effective means of handling food products in order to ensure food safety.
As discussed briefly above, food manufacturers use different technologies to eliminate, retard, or prevent microbial growth, such as heating. Even though heat is very efficient in killing bacteria, it also destroys some nutrients, flavors, or textural attributes of food products.
Effective sanitation depends on the combination of product and sanitation process type, and not all of the currently available technologies can deliver an effective reduction of microorganisms and at the same time prevent product or environmental degradation. Refrigeration is an effective and popular means to slow down the growth of unwanted microbes and enzymatic reactions in foods. Therefore, the shelf life and keeping quality of refrigerated food is extended. Some common ways of chilling food include the use of mechanical refrigeration equipment, ice, and dry ice.
Dry ice is solid or frozen carbon dioxide that is frequently used as an expendable refrigerant. Dry ice converts from a solid directly to a gas in the process known as sublimation. Water ice is another traditional expendable refrigerant, but has the disadvantage of converting to water after the ice melts. Dry ice is much denser and colder than traditional ice with a heat removal capability of approximately 254 btu/lb. Dry ice at atmospheric pressure is −109.3° F. (−78.5° C.) in comparison to traditional water ice 32° F. (0° C.). Dry ice sublimes by going directly from a solid to a gas without passing through the liquid stage. The cold temperature of dry ice and the fact that it leaves no residue like water ice makes it an excellent refrigerant for the transportation of chilled or frozen products. For example, the shipments that must remain frozen during transportation can be packed with dry ice. The contents will be frozen when they reach their destination and there will be no messy liquid left over like traditional water ice.
Dry ice is generally stored in insulated containers prior to use to reduce the rate of sublimation. Losses due to ambient heat typically average 1–2%/day under ideal storage conditions. Based on storage or conditions of use the sublimation rate can be as high as 50%/day. A pound of dry ice after sublimation will convert to 8.5 cubic feet of carbon dioxide gas.
Unfortunately, while refrigeration can retard microbial growth, such treatment does not kill bacteria. Accordingly, microorganisms can still survive through refrigeration, and worse, some microorganisms can still grow and produce harmful substances during refrigerated storage. Upon fumigation or other chemical treatment, another level of health problems may be created or the quality of the treated food may deteriorate. For example, chlorine has been widely used as a sanitizer of choice since World War I. However, concerns regarding the safety of carcinogenic and toxic by-products of chlorine, such as chloramines and trihalomethanes, have been raised in recent years.
Ozone, an unstable, colorless gas with a distinct odor has been proven to work more effectively on spoilage microorganisms than a classic disinfectant such as chlorine. Due to its instability, the three oxygen molecules of ozone break apart to form one diatomic oxygen molecule and another free oxygen radical. This free oxygen radical attacks the cell wall and oxidizes it thus increasing the chance of permeability to the inner surfaces of the cell. This reaction of ozone on cell structures is irreversible; therefore the cells either become attenuated or die. Historically, ozone has been widely used for water treatment since the early 1900's. Some well-known applications include disinfection of swimming pools, spas, cooling towers, and sewage plants. Ozone is normally produced by UV radiation with wavelengths below 200 nm or by the corona discharge method that requires high electric energy.
Ozone has been used as a disinfectant/oxidant in the food industry for the past several decades. It has been well applied to bulk storage (in a “room” type of storage facility) of produce (e.g. apples) or to disinfect water (e.g. municipal water or waste water treatment). Also, processes have been developed using ozone solutions (by injecting ozone gas through water) to sanitize/disinfect food products. Some examples of using ozone for sanitizing food products can be found in U.S. Pat. No. 3,341,280 for sterilizing particulate food materials; U.S. Pat. No. 4,849,237 which utilizes ozonated water for sanitizing poultry carcasses; U.S. Pat. No. 5,011,699 which sterilizes food stuffs in a processing room with the aid of a mixture of ozone gas and carbon dioxide gas and/or nitrogen gas; U.S. Pat. No. 5,405,631 directed to sanitizing citrus fruit with ultraviolet radiation and ozone generation; U.S. Pat. No. 6,210,730 directed to a method for treating perishable meat products, including the steps of chilling the meat product, exposing the chilled meat product to a chilled gas mixture including ozone, and thereafter removing the chilled gas and exchanging that gas with a mixture containing a high oxygen fraction; and U.S. Pat. No. 6,458,398 which is directed to reducing the microbial population of food in a container by the application of both a surfactant and ozone-containing wash liquor to the food.
While ozone is highly water soluble and thus generally more effective in water, it can be used effectively in the air as well, attacking yeasts and fungi as well as bacteria. In this regard, for nearly a century, ozone has been used as a food preservation agent for a wide variety of perishable food items. Among the food items not mentioned previously and potentially preserved by ozonation include potatoes, eggs, cheeses, bananas, berries, meats, carrots, onions, and peaches. Ozone dissolved in water has also been used in food storage—including the preservation of fish in ozonated ice.
Carbon dioxide has natural properties that tend to inhibit the growth of bacteria. These properties are use in controlled atmospheric packaging for preserving food products. Carbon dioxide, however, is not as effective nor as efficient as ozone at destroying bacteria. It would be useful, therefore, to combine the cooling properties of solid dry ice with the pathogen destruction capability of ozone.
JP 071002240 describes a process to prepare a solid oxidizing agent containing ozone and chlorine to simultaneously provide the strong oxidizing property of ozone and continuous oxidizing capability of chlorine to achieve an effective means for disinfection, sanitation, sterilization, prevention of food spoilage, deodorization, etc. Several methods of preparation are provided:                1. Solid oxidizing agent formed by combining ices of ozonated/chlorinated water and dry ice (CO2) and solidified.        2. Solid oxidizing agent formed by combining ices of ozonated water, ices of chlorinated water, and dry ice (CO2).        3. Regarding the oxidizing agent described under 1. Oxidizing agent characterized by its powdered form.        
4. Regarding the oxidizing agent described under 1. Oxidizing agent formed into various specific sizes and shapes.
JP 08107925 is similar to the above and is directed to a solid oxidizing agent comprising a mixture of ice of ozonated water and dry ice in a powdered form or other specific shape. The solid oxidizing agent is prepared by mixing powdered ice of ozonated water and powdered dry ice. The powdered mixture can then be custom made to a specific shape and size. The composition can be used for disinfection, sanitation, sterilization, water purification, and odor removal. Prevention of spoilage and odor of fresh foods is disclosed.
JP 3-217294 discloses a method of manufacturing ozonated water by absorption of ozone in water containing carbon dioxide or carbonic compounds. The objective of the invention is to increase the concentration of ozone into water in as much as high ozone concentrations in water cannot be achieved by conventional techniques which simply dissolve ozone in the water. Accordingly, in this patent, carbon dioxide gas is flushed into water to produce CO2-saturated water. An ozone gas mixture is then flushed into the CO2-saturated water to form ozonated ice. Similarly, sodium bicarbonate-saturated water was formed and then ozone was flushed into the carbonated water. The invention is stated as enabling the manufacturer of ozonated water and ice at higher ozone concentrations than conventional manufacturing methods. The ozone-containing composition in solid form can be used for sanitation purposes and for preserving fresh foods.
SU 1274645 by Rukavishni et al describes a method to prolong the storage life and reduce produce losses of agricultural crops. As an example, rose petals are placed for storage at a low positive temperature, in a hermetically sealed polymeric container. Before loading the petals, the container is treated with an air-ozone mixture with an ozone dose factor of 0.1 mg/1 min. Dry ice is placed in the container, at a rate of 0.9 g per kg of stored produce. The rose petals are then loaded.
JP 09249510 discloses a method of controlling the emission of ozone from silica gel having adsorbed ozone. The silica gel having adsorbed ozone is packed in a bag formed from a gas tight material and having a gas communicating hole. The bag is wrapped with dry ice so that as the dry ice sublimes, the temperature inside the bag increases and allows the desorption of the ozone gas. The ozone gas is released from the bag through the hole.